Led package using phosphor containing elements and light source containing same

ABSTRACT

A light-emitting diode package is described comprising a body including a hollow having a rim that extends outwardly from an open end of the hollow. A light emitting diode is positioned in the hollow and opposite the open end. A nongaseous transparent optical medium fills the hollow and a phosphor-containing element (PCE) is disposed over the hollow sealing the open end. The PCE has a solid body and a lateral portion including a periphery and dividing a top and a bottom. The bottom of the PCE is convex and in contact with the nongaseous transparent optical medium and the periphery of the PCE is in contact with the rim.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of co-pending applicationSer. No. 12/211,325, filed Sep. 16, 2008, the disclosure of which ishereby incorporated by reference.

TECHNICAL FIELD

This invention relates to lighting devices and more particularly tolighting devices employing light emitting diodes (LED or LEDs).

BACKGROUND OF THE INVENTION

An increasing number of lighting devices utilizing LEDs have beenintroduced in the recent past. Many of these devices serve asreplacements for incandescent or fluorescent lamps. Since most LEDs emitlight in a very narrow range (most LEDs are considered to be singlecolor emitters) it has been necessary to combine various colors (e.g.,for example, red, green and blue) to provide white light. Recentadvances in LEDs have provided LEDs that emit strongly in the blue andUV range such that, when combined with phosphors that emit in the yellowregion of the spectrum, provide an acceptable version of white light.Current methods of providing the phosphor component include applying aphosphor-containing silicone encapsulant; phosphor-coated orphosphor-filled plastic sheets; or phosphor-ceramic compositions. In allof these former constructions it is very difficult to control thedimensions of phosphor-containing elements. Also, since many LED devicesinclude a hollow package, which is subsequently filled with atransparent optical medium, the occasional introduction of air bubblesat the interface between the phosphor-containing element and the opticalmedium presents the industry with maintenance and quality controlissues.

SUMMARY OF THE INVENTION

It is, therefore, an object of the invention to obviate the aboveenumerated disadvantages of the prior art.

It is another object of the invention to enhance the operation of LEDdevices.

Yet another object of the invention is the improvement of qualitycontrol in LED devices.

These objects are accomplished, in one aspect of the invention, by theprovision of a light-emitting diode package comprising a body includinga hollow having a rim that extends outwardly from an open end of thehollow. A light emitting diode is positioned in the hollow and oppositethe open end. A nongaseous transparent optical medium fills the hollowand a phosphor-containing element (PCE) is disposed over the hollowsealing the open end. The PCE has a solid body and a lateral portionincluding a periphery and dividing a top and a bottom. The bottom of thePCE is convex and in contact with the nongaseous transparent opticalmedium and the periphery of the PCE is in contact with the rim.

In another aspect of the invention, there is provided a light sourcecomprising an array of light emitting diodes. Each light emitting diodeis positioned in a hollow having an outwardly extending rim. A pluralityof phosphor-containing elements (PCE) is provided with each PCE disposedabove a respective light emitting diode. A nongaseous transparentoptical medium is disposed between each PCE and its respective lightemitting diode. Each PCE comprises a solid body having a lateral portiondividing a top and a bottom. The bottom of each PCE is convex and itslateral portion has a periphery that may include at least one ventingaperture. The bottom of each PCE in contact with the nongaseoustransparent optical medium with its periphery in contact with the rim.

In a further aspect of the invention, the light source is a colormodification assembly that comprises a plurality of PCEs at least someof which contain phosphors selected from the group of red, yellow, blueand green emitting phosphors.

The invention thus provides accurate dimensional control of the PCEsand, with the proper selection of PCEs for the color modificationassembly, a wide control of the color output of the device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an embodiment of the invention;

FIG. 2 is an elevation view of a PCE employable with the invention;

FIG. 3 is an exploded perspective view of an LED package with a PCE;

FIG. 4 is an exploded sectional view of an LED package before assembly;

FIG. 5 is a similar view of the assembled unit.

FIG. 6A is an elevation view of an alternate embodiment of theinvention;

FIG. 6B is a plan view of the bottom of the embodiment of FIG. 6A;

FIG. 7 is a diagrammatic, perspective view of an assembly of theinvention;

FIG. 8 is a sectional, elevation view of yet another embodiment.

DETAILED DESCRIPTION OF THE INVENTION

For purposes of this application it is to be understood that when anelement or layer is referred to as being “on,” “connected to” or“coupled to” another element or layer, it can be directly on, connectedto or coupled to the other element or layer or intervening elements orlayers may be present. In contrast, when an element is referred to asbeing “directly on,” “directly connected to” or “directly coupled to”another element or layer, there are no intervening elements or layerspresent. Like numbers refer to like elements throughout. The term“and/or” includes any and all combinations of one or more of theassociated listed items.

Although the terms “first,” “second,” “third” etc. may be used todescribe various elements, components, regions, layers and/or sections,these elements, components, regions, layers and/or sections are not tobe limited by theses terms as they are used only to distinguish oneelement, component, region, layer or section from another element,component, region, layer or section. Thus, a first element, component,region, layer or section could be termed a second element, component,region, layer or section without departing from the scope and teachingsof the present invention.

Spatially relative terms, such as “beneath,” below,” upper,” “lower,”“above” and the like may be used herein for ease of description todescribe one element or feature's relationship to another element(s) orfeature(s) as illustrated in the drawings. These spatially relativeterms are intended to encompass different orientations of the device inuse or operation in addition to the orientation shown in the drawings.For example, if the device in the drawings is turned over, elementsdescribed as “below” or “beneath” other elements or features would thenbe oriented “above” the other elements or features. Thus, the exemplaryterm “below” can encompass both an orientation of above and below. Thedevice may be otherwise oriented (rotated 90 degrees or at otherorientations) and the spatially relative descriptors used hereininterpreted accordingly.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention.For example, as used herein, the singular forms “a,” “an” and “the” areintended to include the plural forms as well, unless the context clearlyindicates otherwise. It will be further understood that the terms,“comprises” and/or “comprising,” when used in this specification,specify the presence of stated features, integers, steps operations,elements, and/or components, but do not preclude the presence oraddition of one or more other features, integers, steps, operations,elements, components, and/or groups thereof.

For a better understanding of the present invention, together with otherand further objects, advantages and capabilities thereof, reference ismade to the following disclosure and appended claims taken inconjunction with the above-described drawings.

Referring now to the drawings with greater particularity, there is shownin FIGS. 1 and 2 a light source 10 comprising an array 11 of lightemitting diodes 12 appropriately fixed to a suitable substrate 13. Thelight emitting diodes are each connected to an electrical power source(not shown) through at least wire 12 a. A plurality ofphosphor-containing-elements 14 (PCE or PCEs), only one of which isshown in FIG. 1 in the interest of clarity, is associated with the array11 of light emitting diodes 12 in a one-to-one relationship, each of thePCEs 14 having a solid body 15 comprising a lateral portion 16 dividinga top 18 and a bottom 20, the bottom 20 being convex. The lateralportion 16 includes a periphery 17 preferably having at least oneventing aperture 19 therein. Each PCE 14 is disposed above itsrespective light emitting diode 12 such that the light emitted by thelight emitting diode is directed at the bottom 20 of PCE 14. The top 18of the PCE 14 can be planar, convex or any other configuration and, ifconvex, have a degree of curvature, whereby it can provide a lensfunction, if desired. As an example, in FIGS. 3-5 the top 18 is shown asbeing hemispherical.

In a preferred embodiment of the invention, each of the light emittingdiodes 12 emit a blue light in the range of 430-470 nm and the PCEs aresolid, phosphor-filled, injection-molded silicone, polycarbonates,acrylics or similar material. Injection molding is preferred as thistechnique allows for very precise control of the PCE geometry. Becauseof the small size of the PCE, typically in the range of 1 mm to 20 mm onedge, a significantly smaller amount of phosphor will be utilized,generally in the range of 4-50 weight percent, although the actualamount will depend on the package on which it is mounted and the colorpoint desired.

When activated by the light emitted from said light emitting diodes 12,the PCEs 14 emit light having a different, and generally longer,wavelength than the light emitted by the light emitting diodes. Thisallows for the provision of a color modification assembly 30, as shownin FIG. 7, which comprises a plurality of PCEs 14 at least some of whichcontain phosphors selected from the group of red, yellow, blue and greenemitting phosphors. A plurality of PCEs 14 which emit in differentcolors, for example, in the red, yellow, blue and green areas of thespectrum (and are represented diagrammatically in FIG. 7 as R₁₄, Y₁₄,B₁₄ and G₁₄ respectively), can be assigned to bins 31 in acompartmentalized container 32. Since the PCEs 14 are made independentlyof the LED package, the PCEs can be matched to a particular package tomaximize the package wavelengths that can be used while minimizing thecolor variability between the packages.

Because the initial wavelength available from the LEDs is in the rangeof 430-470 nm, it is preferred that the phosphors selected for theassembly be excited to emission by wavelengths in that range.

Table I illustrates the approximate C.I.E. color coordinates ofexemplary phosphors that can be employed with the invention, all ofthese phosphors being excited to luminescence by radiation in the430-470 nm range, such as that available from an InGaN LED.

TABLE I C.I.E. Color PHOSPHOR Coordinates (x, y) Y₃Al₅O₁₂:Ce³⁺ (0.45,0.52) Y₃Al_(5−x)Ga_(x)O₁₂:Ce³⁺ (0.44, 0.53) (Lu,Y)₃(Al,Ga)₅O₁₂:Ce³⁺(0.42, 0.56) Ca₈Mg(SiO₄)₄Cl₂:Eu²⁺ (0.20, 0.62) SrSi₂O₂N₂:Eu²⁺ (0.36,0.60) Ca_(1−x)Sr_(x)Si₂O₂N₂:Eu²⁺ (0.38, 0.57) SrBaSi₂O₂N₂:Eu²⁺ (0.45,0.58) Ca₂Si₅N₈:Eu²⁺ (0.58, 0.39) Ca_(5−d)Al_(4−2d)St_(8+2d)N₁₈Eu²⁺(0.59, 0.39) Sr_(2−x)Ca_(x)Si₅N₈:Eu²⁺ (0.65, 0.32)Ba_(2−x)Sr_(x)Si₅N₈:Eu²⁺ (0.59, 0.37)

A representative light-emitting diode package 40 is shown in FIGS. 3-5and comprises a body 42 with a hollow 44 having a rim 45 extendingoutwardly from open end 48. The open end 48 has a diameter D₁. A lightemitting diode 12 is positioned in the hollow 44 and a nongaseoustransparent optical medium 46, such as silicone, epoxy or other opticaladhesive, fills the hollow 44. A PCE 14 seals the hollow 44 with theperiphery 17 of the PCE 14 in contact with the rim 45 and completes thepackage 40. The convex bottom 20 of the PCE displaces some of thenongaseous transparent optical medium 46 and insures that no air bubblesexist at the interface. It is also advisable to place a vent or vents 19about the periphery 17 of the lateral portion 16 to further aid in theremoval of any air bubbles. The vents can take the form of apertures 19as shown in FIGS. 3-5 or grooves 19 a as shown in the embodimentdescribed below.

In an alternate embodiment, shown in FIGS. 6A and 6B, the PCE 14 can beprovided with longitudinal grooves 19 a in place of or in addition tothe apertures 19. As with previous embodiments the convex bottom 20 hasa diameter D₂ wherein D₂ preferably is approximately equal to D₁ so thatany air that might be otherwise trapped underneath the PCE 14 is shuntedto the grooves. Moreover, the grooves allow for any excess of thetransparent medium 46 displaced by the convex bottom 20 to flow into thegrooves to relieve any pressure when seating the PCE 14 to the package40 and also provide for additional bonding between the periphery and therim.

In yet another embodiment, shown in FIG. 8, the lateral portion 16 ofthe solid body 15 can terminate in a curb or lip 50 that fits about theexternal edge of the body 42 to aid in alignment of the PCE 14 to thebody 42 of package 40.

The PCEs can be provided on an individual basis or with an assembly thatallows a considerable range of color matching or correcting. Theperipheral rim of the lateral portion, together with the convex bottomand the venting apertures assures a good bond with no distorting airbubbles in the transparent optical medium or the interface between themedium and convex bottom.

While there have been shown and described what are at present consideredto be the preferred embodiments of the invention, it will be apparent tothose skilled in the art that various changes and modifications can bemade herein without departing from the scope of the invention as definedby the appended claims.

GLOSSARY OF REFERENCE NUMERALS USED HEREIN

-   10 light source-   11 array of diodes-   12 diodes-   12 a wire-   13 substrate-   14 phosphor containing elements (PCEs)-   15 solid body of PCEs-   16 lateral portion of 15-   17 periphery of 16-   18 top of 16-   19 venting aperture in 17-   19 a venting groove in 17-   20 bottom of 16-   30 assembly-   31 bins-   32 container-   40 light-emitting diode package-   42 body of 40-   44 hollow in 42-   46 nongaseous transparent optical medium-   48 open end-   50 curb on 16-   D₁ diameter of 48-   D₂ diameter of 20

1. A light-emitting diode package 40 comprising: a body 42 including ahollow 44 having a rim 45, said rim extending outwardly from an open end48 of said hollow 44; a light emitting diode 12 positioned in saidhollow 44 and opposite said open end 48; a nongaseous transparentoptical medium 46 filling said hollow 44; and a phosphor-containingelement (PCE) 14 disposed over said hollow 44 and sealing said open end48, said PCE 14 having a solid body 15 and a lateral portion 16including a periphery 17 dividing a top 18 and a bottom 20, said bottom20 being convex and in contact with said nongaseous transparent opticalmedium 46 and said periphery 17 being in contact with said rim
 45. 2.The light-emitting diode package 40 of claim 1 wherein said periphery 17includes at least one venting aperture
 19. 3. The light-emitting diodepackage 40 of claim 1 wherein said top 18 is convex.
 4. Thelight-emitting diode package 40 of claim 3 wherein said top 18 has agreater convexity than said bottom
 20. 5. The light-emitting diodepackage 40 of claim 1 wherein said light emitting diode 12 emits in therange of 430-470 nm.
 6. The light-emitting diode package 40 of claim 1wherein said PCE 14 contains at least one phosphor selected from thegroup of red-, yellow-, blue- and green-emitting phosphors.
 7. Thelight-emitting diode package 40 of claim 1 wherein said open end 48 hasa diameter D₁ and said convex bottom 20 has a diameter D₂ which isapproximately equal to D₁.
 8. The light-emitting diode package 40 ofclaim 7 wherein said periphery 17 includes at least one longitudinalgroove 19 a.
 9. The light-emitting diode package 40 of claim 1 whereinsaid lateral portion 16 of said solid body 15 terminates in a curb 50.10. A light source 10 comprising: an array 11 of light emitting diodes12; each light emitting diode 12 being positioned in a hollow 44 havingan outwardly extending rim 45; a plurality of phosphor-containingelements 14 (PCE), each PCE 14 disposed above a respective lightemitting diode 12; a nongaseous transparent optical medium 46 disposedbetween each PCE 14 and its respective light emitting diode 12; saidPCEs 14 comprising: a solid body 15 having a lateral portion 16 dividinga top 18 and a bottom 20, said bottom 20 being convex, said lateralportion 16 having a periphery 17, said bottom 20 being in contact withsaid nongaseous transparent optical medium and said periphery being incontact with said rim.
 11. The light source 10 of claim 10 wherein saidlight emitting diodes are disposed in bins in a compartmentalizedcontainer.
 12. The light source 10 of claim 10 wherein said hollow 44has an open end 48 having a diameter D₁ and said convex bottom 20 has adiameter D₂ which is approximately equal to D₁.
 13. The light source 10of claim 10 wherein said periphery 17 includes at least one ventingaperture
 19. 14. The light source 10 of claim 13 wherein said ventingaperture 19 is a longitudinal groove 19 a.